Moon Stonein Pokémon Polished Crystal

Evolves certain kinds of Pokémon. Works on the Nidoran line, along with Clefairy, Jigglypuff... and a few others! You'll find these in Mt. Moon, Tohjo Falls, and some other caves! Wild Clefairy line holds them too if you want to farm. I usually evolve my Nidorino/rina as soon as I get a Moon Stone since Nidoking and Nidoqueen can learn way more TMs than their pre-evos. No reason to wait on those.